JPH0959487A - Conductive resin paste - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a conductive resin paste which can be cured at 200 deg.C or lower within 30sec or shorter. SOLUTION: The paste comprises (A) silver particles, (B) an epoxy resin which is liquid at ordinary temp., (C) a compound having at least two cyanate groups per molecule and represented by the formula (wherein R1 is CH2 , CH(CH3 ), or C(CH3 )2 , R2 and R3 each is H of CH3 , and n is 0 or a positive integer), and (D) a metal complex as essential components. The amounts of the components (A), (B), and (C) are 60-85wt.%, 0.1-30wt.%, and 9-39wt.%, respectively, based on the whole paste.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a conductive resin paste for adhering semiconductor elements such as IC and LSI to a substrate such as a metal frame.

[0002]

2. Description of the Related Art In a process of bonding a semiconductor element to a metal frame, that is, in a so-called die bonding step, it is necessary to mount the semiconductor element on the metal frame and then harden it by a method using a conductive resin paste. Conventionally, curing in a batch system using an oven has been the mainstream. However, in recent years, a curing furnace has been installed next to the die bonder that mounts semiconductor elements on a metal frame, and the steps of die bonding, curing, and wire bonding are performed continuously on the same line, and an in-line method that improves productivity is adopted. ,
There is a tendency to increase further in the future. This in-line method has a limitation on the curing time as compared with the conventional batch method. For example, the curing time is 150 to 200 in the conventional batch method.
The temperature was 60 to 120 minutes at 0 ° C, but it should be 15 to 90 seconds at 150 to 200 ° C in the in-line method.
Further, in recent years, a copper frame has been adopted, and oxidation of the frame surface due to the temperature during curing significantly lowers the reliability of semiconductor products. Therefore, there is an increasing demand for a conductive resin paste that cures at a lower temperature. In order to cope with these problems, an amine-based curing agent that cures in a short time has been used as a curing agent in a conductive resin paste that uses an epoxy resin. However, a conductive resin paste using an amine-based curing agent cannot obtain a good cured product at a temperature of 180 ° C. or lower, has poor adhesive strength at high temperatures, and cannot be cured at lower temperatures.

[0003]

DISCLOSURE OF THE INVENTION The present invention provides a conductive resin paste having excellent curability under the conditions of 180 ° C. or lower and 60 seconds or less.

[0004]

The present invention provides (A) silver powder,
(B) Epoxy resin that is liquid at room temperature, (C) A compound having at least two cyanate groups in one molecule represented by formula (1), and (D) a conductive resin paste containing a metal complex as an essential component. In the total conductive resin paste, the component (A) is 60 to 85% by weight, and the component (B) is 0.1 to
It is a conductive resin paste containing 30% by weight and 9 to 39% by weight of the component (C).

[0005]

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The compound of the formula (1) used in the present invention having at least two or more cyanate groups in one molecule (hereinafter, referred to as
The cyanate group (referred to as a cyanate compound) easily undergoes a trimerization reaction by heating in the presence of a metal complex to form a triazine ring. Due to the formation of the triazine ring, the cyanate compound has a three-dimensional structure, so-called network structure, and is cured. Also, due to the formation of this triazine ring, compared to the epoxy resin used in the conventional conductive resin paste,
High glass transition temperature. That is, the glass transition temperature of the epoxy resin is about 120 to 150 ° C, whereas that of the cyanate compound is about 180 to 220 ° C. When the glass transition temperature is high, high adhesive strength when heated can be obtained. That is, by using the conductive resin paste of the present invention, it is possible to prevent the chip from slipping in the wire bonding process at the time of assembling the IC. The cyanate compound of the present invention is represented by the formula (1), more preferably the formula (2), in which the viscosity of the compound represented by the formula (1) is too high and the paste coating operation It significantly reduces the sex. The amount of the cyanate compound blended is 9 to 39% by weight, and if it is less than 9% by weight, the high adhesive strength characteristic of the cyanate compound cannot be obtained. If it exceeds 39% by weight or if it is not used in combination with an epoxy resin, the cyanate compound crystallizes during freezing storage and the viscosity becomes extremely high, deteriorating the coating workability.

[0007]

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The in-line type conductive resin paste using an epoxy resin uses an amine-based curing agent having excellent reactivity, such as imidazoles and primary amines, as a curing agent. Has a curing temperature of 180
If the temperature is lower than 0 ° C, good curability is not exhibited, and the adhesive strength at high temperature is extremely low. However, with the conductive resin paste using the cyanate compound of the present invention, a good cured product can be obtained even at a curing temperature of 180 ° C. or lower, and the adhesive strength at high temperatures is also high. Further, in such a cyclization reaction of a cyanate compound, it is general to use a metal complex as a catalyst and a phenol having active hydrogen, particularly nonylphenol, as a cocatalyst. However, when the conductive resin paste is used, if there is a rapid change in viscosity, the coating workability deteriorates, so pot life is important. In a conductive resin paste using a cyanate compound, the reaction proceeds rapidly if phenols are added even in a very small amount, and the pot life is reduced,
In the present invention, phenols such as nonylphenol, which is a co-catalyst for the cyclization reaction of the cyanate compound, is not added because it significantly deteriorates the coating workability.

The silver powder used in the present invention is preferably 50 μm or less. If it exceeds 50 μm, needle clogging is likely to occur during paste application. The field of use of ionic impurities such as sodium and chlorine contained in silver powder is related to semiconductors, and it is desirable to be as small as possible in view of the reliability of LSI and the like.
It is desirable that the concentration be 20 ppm or less after extraction at 20 ° C. for 20 hours. The silver powder may have a flake shape, a dendritic shape, a spherical shape, etc., and may be used alone or as a mixture. The content of silver powder in the total conductive resin paste is 60 to 85% by weight.
If it is less than wt%, satisfactory conductivity cannot be obtained. On the other hand, if it exceeds 85% by weight, the viscosity becomes high and the coating workability deteriorates. The epoxy resin used in the present invention is limited to a liquid at ordinary temperature, but if it is not liquid at ordinary temperature, a larger amount of solvent is required in kneading with silver powder. The solvent causes generation of bubbles and reduces the adhesive strength of the cured product. Epoxy resin content is 0.1-30% by weight
If less than 0.1% by weight, crystallization of cyanate cannot be prevented during frozen storage. If it exceeds 30% by weight, high adhesiveness cannot be obtained. Examples of the epoxy resin used in the present invention include bisphenol A, bisphenol F,
Polyglycidyl ether obtained by reaction of phenol novolac resin and epichlorohydrin at room temperature, alicyclic epoxy such as vinylcyclohexene dioxide, dicyclopentadiene oxide, alicyclic diepoxy-adipide, and n-butylglycidyl ether. , Versidic acid glycidyl ester, styrene oxide phenyl glycidyl ether, butyl phenyl glycidyl ether, creglycidyl ether, and dicyclopentadiene diepoxide, which are commonly used as diluents for epoxy resins.

The cyanate compound used in the present invention also reacts with the above-mentioned epoxy resin and is effective as a curing agent for epoxy, but in the present invention, a general curing agent for epoxy resin may be added. As the curing agent to be used, those generally having active hydrogen in the molecule such as phenols, imidazole and dicyandiamide are desirable,
As mentioned above, phenols are not desirable because they reduce pot life. The metal complex used in the present invention includes, for example, metal naphthenates such as cobalt, zinc, iron, copper, chromium, manganese, nickel and titanium, salts of acetylacetonate or its derivative, various carboxylates, organic compounds such as alkoxides. There are metal salts, which may be used alone or in combination. Further, additives such as a curing accelerator, a pigment and an antifoaming agent can be used in the resin composition of the present invention, if necessary. The production method of the present invention includes, for example, pre-kneading each component, kneading using a three-roll mill, obtaining a paste, and defoaming under vacuum.

The present invention will be specifically described below with reference to examples. Examples 1 to 7 Diglycidyl ether obtained by the reaction of bisphenol A and epichlorohydrin (liquid at room temperature with an epoxy equivalent of 180, hereinafter epoxy resin), bisphenol A type cyanate ester as a cyanate compound [R ₁ of formula (2) is C (CH ₃ ) ₂ , R ₂ and R ₃ are H, a molecular weight of 278, hereinafter cyanate compound A], or a bisphenol AD type cyanate ester [R ₁ of the formula (2) is CH.
CH ₃ , R ₂ and R ₃ were H, molecular weight 306, cyanate compound B] below, and cobalt naphthenate or cobalt acetylacetonate salt was used as the metal complex.
Further, silver powder having a maximum particle size of 50 μm or less was mixed in a ratio shown in Table 1 and kneaded with a three-roll mill to obtain a conductive resin paste. 2m of this conductive resin paste in a vacuum chamber
After defoaming at mHg for 30 minutes, various performances were evaluated by the methods described below. Table 1 shows the evaluation results. Viscosity: Using an E-type viscometer (3 ° cone), 25 ° C, 2.
Measured value at 5 rpm. The measured value after standing for 3 days in a constant temperature bath at 25 ° C was taken as the viscosity after 3 days. Volume resistivity: paste 4 mm wide on glass slide,
The volume resistivity of the cured product after being applied to a thickness of 30 μm and cured on a 170 ° C. hot plate for 30 seconds was measured. Adhesive strength at 350 ° C. heat: A 2 mm square silicon chip was mounted on a copper frame using a paste, and cured on a 170 ° C. hot plate for 30 seconds. After curing, the die shear strength under heat at 350 ° C. was measured using a push-pull gauge.

Comparative Examples 1 to 6 Conductive resin pastes were prepared with the compounding ratios shown in Table 2 in exactly the same manner as in the examples. In Comparative Example 1, since the epoxy compound was not added, the cyanate compound started to crystallize, and the viscosity of the conductive resin paste was increased. Comparative Example 2
However, sufficient curability could not be obtained because the amount of the cyanate compound was small. In Comparative Example 3, sufficient conductivity could not be obtained because the amount of silver powder was small. In Comparative Example 4, since the amount of silver powder was large, the viscosity was high and the coating workability was deteriorated. In Comparative Example 5, since no metal complex was added, sufficient curability could not be obtained. In Comparative Example 6, the addition of nonylphenol, which is a co-catalyst, significantly reduced the pot life.

[0013]

[Table 1]

[0014]

[Table 2]

[0015]

Since the conductive resin paste of the present invention is particularly excellent in curability, it can be cured at 200 ° C. or lower for 30 seconds or less, and has a highly reliable characteristic which has never been obtained. In addition, it has good workability during dispense application, and has less ionic impurities such as sodium and chlorine.
It can be used for bonding a semiconductor element such as an IC or an LSI to an organic substrate such as a metal frame of two alloys, a ceramic substrate, or a glass epoxy.

Claims (2)

[Claims] 1. An (A) silver powder, (B) an epoxy resin which is liquid at room temperature, (C) a compound having at least two cyanate groups in one molecule represented by the formula (1), and (D).
A conductive resin paste containing a metal complex as an essential component, wherein the component (A) is 60 to 85 in the total conductive resin paste.
%, The component (B) is 0.1 to 30% by weight, and the component (C) is 9 to 39% by weight. Embedded image 2. The conductive resin paste according to claim 1, wherein the component (C) has the formula (2). Embedded image